From fcbd68fd6556b2f05c47a0399c2e6fd7689bfdab Mon Sep 17 00:00:00 2001
From: Adrian Chelaru <che.adrian@yahoo.com>
Date: Wed, 8 Feb 2023 16:14:24 +0000
Subject: [PATCH 1/5] cache the value of file_inode() in struct file

---
 fs/file_table.c    | 2 ++
 fs/open.c          | 2 ++
 include/linux/fs.h | 6 ++++++
 3 files changed, 10 insertions(+)

diff --git a/fs/file_table.c b/fs/file_table.c
index 70f2a0fd..768cf946 100644
--- a/fs/file_table.c
+++ b/fs/file_table.c
@@ -176,6 +176,7 @@ struct file *alloc_file(struct path *path, fmode_t mode,
 		return NULL;
 
 	file->f_path = *path;
+	file->f_inode = path->dentry->d_inode;
 	file->f_mapping = path->dentry->d_inode->i_mapping;
 	file->f_mode = mode;
 	file->f_op = fop;
@@ -259,6 +260,7 @@ static void __fput(struct file *file)
 		drop_file_write_access(file);
 	file->f_path.dentry = NULL;
 	file->f_path.mnt = NULL;
+	file->f_inode = NULL;
 	file_free(file);
 	dput(dentry);
 	mntput(mnt);
diff --git a/fs/open.c b/fs/open.c
index 3f1108b1..2c60e49b 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -660,6 +660,7 @@ static struct file *__dentry_open(struct dentry *dentry, struct vfsmount *mnt,
 		f->f_mode = FMODE_PATH;
 
 	inode = dentry->d_inode;
+	f->f_inode = dentry->d_inode;
 	if (f->f_mode & FMODE_WRITE) {
 		error = __get_file_write_access(inode, mnt);
 		if (error)
@@ -733,6 +734,7 @@ cleanup_all:
 	file_sb_list_del(f);
 	f->f_path.dentry = NULL;
 	f->f_path.mnt = NULL;
+	f->f_inode = NULL;
 cleanup_file:
 	put_filp(f);
 	dput(dentry);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index b827a8fd..a609ade3 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2221,6 +2221,12 @@ static inline bool execute_ok(struct inode *inode)
 	return (inode->i_mode & S_IXUGO) || S_ISDIR(inode->i_mode);
 }
 
+static inline struct inode *file_inode(struct file *f)
+{
+	/* return f->f_path.dentry->d_inode; / can also use this */
+	return f->f_inode;
+}
+
 /*
  * get_write_access() gets write permission for a file.
  * put_write_access() releases this write permission.
-- 
2.38.3